1. Field of the Invention
The present invention relates to a pulley unit having a one-way clutch. This pulley unit can be provided in, for example, an auxiliary machine driven through a belt by a crank shaft of a vehicle engine. The auxiliary machine may include, for example, air conditioner compressor, water pump, alternator, cooling fan of a vehicle and the like.
2. Description of the Related Art
Various auxiliary machines mounted on a vehicle engine are driven through a belt by a crank shaft of its engine. In case of an alternator, for example, which is one of the auxiliary machines, if it is coupled with an engine crank shaft so as to rotate synchronously therewith, when the rotation speed of the crank shaft drops, power generation capacity of the alternator also drops.
Thus, the inventor of the present invention has considered that by incorporating the aforementioned one-way clutch in a pulley portion of the alternator, when the rotation speed of the crank shaft drops, the rotation of a rotor of the alternator is kept the same by its inertia force so as to intensify power generation efficiency.
In this case, the one-way clutch is interposed between the pulley of the alternator and rotor, and the one-way clutch is changed from a lock state (driving power transmitting state) to a free state (driving power transmission shut-down state) depending on a difference of the rotation between the pulley and rotor. Consequently, the driving power is transmitted or shut down between the pulley and rotor. On one side or both sides of the one-way clutch in an annular space between the pulley and rotor, a rolling bearing for bearing the load and smoothing a rotation of the rotor is provided.
Usually, a sealing member is mounted at an outer end of the aforementioned rolling bearing in the axial direction so as to seal the rolling bearing and one-way clutch from outside. This sealing member forms a non-contact type sealing portion in which an inner periphery or outer periphery opposes an inner or outer wheel of a rolling bearing, rotor or pulley via a minute gap or a contact type sealing portion in which the inner periphery or outer periphery contacts.
In the above described conventional example, because the non-contact type sealing portion or contact type sealing portion by the sealing member is exposed outside, if water is directly splashed over this sealing portion, water is likely to invade through this sealing portion.
To solve this problem, the inventor considered that, for example, a bottomed cylindrical lid was fit to an end portion of a free end of the pulley so as to hide the free end of the pulley from outside. Usually, the pulley is fixed to the auxiliary machine or driving shaft by a bolt and nut and the lid covers an entire end face of the pulley. Thus, when the pulley is installed, the installation of the pulley cannot be carried out until the lid is removed. Further when the pulley is removed, the removal of the pulley cannot be carried out until the lid is removed. Thus, these procedures are troublesome. Although the material of the lid can be synthetic resin so as to save cost, the expansion coefficient of the lid is larger than that of the pulley so that the lid come to slip out easily of the pulley with a generation of heat in the pulley.